1. Field of the Invention
The present invention relates to a control device for a motor fan of a vehicle which cools a condenser for an air conditioner or the like.
2. Description of the Related Art
As a control technology for a motor fan of a vehicle, there is, for example, the one disclosed in Japanese Laid-Open Patent Publication No. 2001-317353.
With this control technology, the greater one of a first duty command value for the motor fan which fulfils the performance requirements for the air conditioning system, and a second duty command value for the motor fan which fulfils the requirements of the engine cooling system, is set first as a first duty target value. And then a second duty target value for the motor fan is calculated which makes the total torque, which is the sum of the torque of the alternator and the torque of the compressor of the air conditioner, become a minimum. And the motor fan is controlled according to that one of the first and the second duty target values which is the larger as a control command values for the motor fan, and thereby, along with maintaining the required performance of the engine cooling system and of the air conditioning system, the fuel economy of the vehicle is improved.
With the above described prior art, the calculation of the torque of the compressor for the second duty target value is performed based upon the pressure of the air conditioner refrigerant and upon the external temperature. Due to this, it is possible to calculate the second duty target value in correspondence to the refrigerant pressure and the external temperature, and it becomes possible to improve the fuel economy, without it being influenced by change of the refrigerant pressure or of the external temperature.
However, since the actual torque of the compressor also varies according to the cooling requirement within the vehicle passenger compartment. Accordingly, the torque of the compressor which has only been calculated from the external temperature and the refrigerant pressure as described above will deviate from the actual torque, if the cooling requirement within the vehicle passenger compartment has changed.
Since, due to this, the second duty target value which has been calculated does not necessarily correspond to the minimum torque, so that the engine does not necessarily drive the motor fan and the compressor at the minimum load, accordingly, the possibility of improving the fuel economy of the vehicle experiences a certain restriction.
The present invention proposes a control device of a motor fan of a vehicle which anticipates enhancement of the fuel economy and also makes possible for the compressor to operate in the ideal state.
A control device for a motor fan of a vehicle, according to the present invention, which controls the motor fan to cool a radiator for engine coolant and a condenser for air conditioner refrigerant, comprises: a first command value calculation section which calculates a first command value for control of the motor fan according to refrigerant pressure; a second command value calculation section which calculates a second command value for control of the motor fan according to coolant temperature; a first target value setting section which sets the greater of the first command value and the second command value as a first target value; a second target value setting section which obtains a second target value for control of the motor fan which corresponds to a total torque which is smaller than a total torque of a torque of an alternator and a torque of a compressor corresponding to the first target value; and a control section which controls the motor fan according to the second target value. And the second target value setting section corrects the total torque of the torque of the alternator and the torque of the compressor based upon a predetermined condition when obtaining the total torque of the torque of the alternator and the torque of the compressor.
Another control device for a motor fan of a vehicle, according to the present invention, which controls a motor fan by duty ratio control to cool a radiator for engine coolant and a condenser for air conditioner refrigerant, comprises: a first command value calculation section which calculates a first command value of duty ratio according to refrigerant pressure; a second command value calculation section which calculates a second command value of duty ratio according to coolant temperature; a first target value setting section which sets the greater of the first command value and the second command value as a first target value of duty ratio; a second target value setting section which calculates a total torque of a torque of an alternator and a torque of a compressor, and sets a duty ratio for which the total torque becomes a minimum as a second target value; and a duty ratio determination section which sets the greater of the first target value and the second target value as a final duty ratio. And the second target value setting section corrects the calculated total torque of the torque of the alternator and the torque of the compressor based upon a rotational speed of a blower fan motor, and sets a duty ratio for which the corrected total torque becomes minimum as the second target value.
Another control device for a motor fan of a vehicle, according to the present invention comprises: an engine; an alternator which is driven by the engine; an air conditioning device of which a compressor is driven by the engine; an electrically driven motor fan which is operated by receiving supply of electrical power generated by the alternator, and which cools the air conditioning device; a discharge pressure detection section which detects a discharge pressure of the compressor; a target discharge pressure setting section which sets a target discharge pressure of the compressor with respect to a cooling performance which is required from the air conditioning device, so that a total of a drive load of the compressor and a drive load of the alternator for obtaining electrical power for operating the electrically driven motor fan becomes a minimum; and a motor fan control section which controls an operation of the electrically driven motor fan so that the discharge pressure of the compressor becomes equal to the target discharge pressure.
A control method for a motor fan of a vehicle, according to the present invention, which controls the motor fan to cool a radiator for engine coolant and a condenser for air conditioner refrigerant, comprises: calculating a first command value for control of the motor fan according to refrigerant pressure; calculating a second command value for control of the motor fan according to coolant temperature; setting the greater of the first command value and the second command value as a first target value; obtaining a second target value for control of the motor fan which corresponds to a total torque which is smaller than a total torque of a torque of an alternator and a torque of a compressor corresponding to the first target value; and controlling the motor fan according to the second target value. And the total torque of the torque of the alternator and the torque of the compressor is corrected based upon a predetermined condition when obtaining the total torque of the torque of the alternator and the torque of the compressor.
Another control method for a motor fan of a vehicle, according to the present invention, which controls the motor fan to cool an air conditioning device of which a compressor is driven by an engine, comprises: detecting a discharge pressure of the compressor; setting a target discharge pressure of the compressor with respect to a cooling performance which is required from the air conditioning device, so that a total of a drive load of the compressor and a drive load of the alternator for obtaining electrical power for operating the motor fan becomes a minimum; and controlling an operation of the motor fan so that the discharge pressure of the compressor becomes equal to the target discharge pressure.